Complexes PhMgBr center dot nMgBr(2)center dot mNEt(3) in the reaction with acetylene

Kinetics of the reaction of acetylene with two phenylmagnesium bromide reag ents of different magnesium bromide content (Br/Mg 1.08 and 1.27) in diethy l ether in the presence of various additions of triethylamine (TEA) were in vestigated. The reagent of average stoichiometry PhMgBr . 2TEA reacts about 20 000 times faster than in the absence of the amine. Elevated content of magnesium bromide in the reagent enhances the accelerating effect of the am ine. The complicated relationships obtained enabled us to draw conclusions on the structure and reactivity of the title complexes. At moderate magnesi um bromide content species 2PhMgBr . MgBr2 dominate and preferentially comp lex with TEA giving solvates more reactive than PhMgBr . TEA, whose formati on takes place at a higher amine content. (C) 1999 Elsevier Science S.A. Al l rights reserved.